The present invention relates to a non-caking, freely flowing, non-caking, abrasion resistant, granular composition of a polymeric phosphate and an ion-exchanging silicate, to a simple and effective process of making same, and to a method of using said composition in washing, rinsing, and cleaning agents, for water softening, and for other purposes.
The requirements for a highly effective washing, rinsing, and cleaning agent to be used in washing, rinsing, and cleaning apparatus are of a highly complex nature due to the peculiarities of the dosing devices in such apparatus, for instance, in dish-washing machines. In order to avoid agglomeration, caking, or lump-formation of the cleaning composition in the dosing- or measuring-chamber and to always assure fully satisfactory flushing or rinsing out of the cleaning agent, the latter is usually employed in the form of a granular composition.
The known washing, rinsing, and cleaning agents contain sodium tripolyphosphate as an essential component. For ecological reasons it has been suggested to replace part of said phosphate-containing builder by water-insoluble, ion-exchanging silicates and more particularly by alkali metal aluminum silicates. Such agents have been described in German Offenlegungsschrift No. 2,412,837. However, using such compounds has the disadvantage that they remain in an unwetted state in water for a relatively long period of time. As a result thereof their action is considerably delayed. When using automatic washing-machines, it has been found that such cleaning-compositions are not fully utilized within the available period of time and/or that unsatisfactory washing results are achieved by the delayed setting free of said agent.
Therefore attempts have been made to improve the wettability of the alkali metal aluminum silicates. A process of producing an ion-exchanging alkali metal aluminum silicate with a hydrophilic surface is described in German Offenlegungsschrift No. 25 10 741. According to said process crystalline alkali metal aluminum silicate is intimately mixed with penta-sodium tripolyphosphate, the mixture is dried, and is comminuted.
The resulting hydrophilic powders, however, frequently do not yield satisfactory results when employed in automatic washing- and dish-rinsing-machines. They readily agglomerate in the dosing-containers, they cannot be flushed or washed out without leaving a residue, and due thereto considerable trouble is encountered during the rinsing-procedure. Granular compositions of sodium tripolyphosphate (designated hereinafter as STPP) and of alkali metal aluminum silicate (designated hereinafter as AAS), although having a well-defined granular structure, are of very limited stability and, as a result thereof, tend to form dust on mixing with additional components of the composition or during compounding. In this case the formation of substantial amounts of dust usually is accompanied by the composition being washed out poorly of the dosing-chamber.
Thus, it is of considerable importance to produce stable, abrasion resistant, non-caking, free flowing, granular compositions based on polymer phosphates and alkali metal aluminum silicates which compositions do not have the above-mentioned disadvantages.
It is also known to improve granulation by the addition of special binding-agents as disclosed in German Offenlegungsschrift No. 20 20 427. However, experiments with such binding-agents, for instance, with carboxy methyl cellulose or gum arabic, were unsuccessful when mixing an alkali metal aluminum silicate with sodium tripolyphosphate.
Furthermore, spraying of a waterglass solution upon a mixture of sodium tripolyphosphate and sodium silicate as suggested in German Offenlegungsschrift No. 2,039,584 for producing stable granular particles were also unsuccesful. It was not possible to obtain in this manner abrasion-resistant, granular compositions.